Internal combustion engine with AT regulator

ABSTRACT

Internal combustion engine with as exhaust pressure regulator ( 10 ) arranged in an exhaust conduit ( 5 ) for regulating the exhaust counter-pressure in the engine cylinders. Upstream of the exhaust pressure regulator, the exhaust conduit communicates via valve means ( 17 ) with the intake side of an air compressor ( 14 ) to make possible pre-charging of the compressor during engine braking.

This application is an 371 of PCT/SE 98/01051, dated Jun. 3, 1998.

BACKGROUND OF THE INVENTION

The present invention relates to an internal combustion engine with ashutter device arranged in an exhaust conduit for regulating the exhaustcounter-pressure in the engine cylinders during engine braking.

It is known that the engine braking power of a vehicle can be increasedwith the aid of a shutter in the engine exhaust manifold. This exhaustpressure regulator provides continuous variation between a completelyopen position and a completely closed position. In the closed position,a counter-pressure can be created during the exhaust stroke of theengine, so that a pressure of up to 3-4 bar is created in the enginecylinders and the exhaust manifold, which increases the braking power ofthe engine during the exhaust stroke. The exhaust pressure regulator canalso be used when the exhaust system is put into communication with thecylinders during the latter portion of the inlet stroke to achieve aninner charging, thus increasing the compression work after cutting offthe communication between the cylinders and the exhaust system.

Vehicles with engines having exhaust pressure regulators are practicallywithout exception heavy vehicles, such as trucks and buses, which have anumber of pneumatically controlled installations and systems, such aspneumatic brakes, air springs etc., which are supplied with compressedair from air tanks charged by an air compressor usually drivenmechanically directly by the engine. The air compressor takes its intakeair from the surrounding atmosphere. The greater the air requirementsthe air consumers have, the greater will be the required capacity of thecompressor and the greater the power is which must be extracted from theengine. Vehicles requiring exceptionally great amounts of compressed airare for example buses, which must be braked many times for stopping atbus stops and traffic lights and which also have pneumatically operateddoors. Buses with air suspensions, which “dip” at bus stops, have extralarge air requirements.

By EP 0 335 086 it is previously known to control a compressed aircompressor driven by the vehicle engine via clutch, depending on theoperating state of the vehicle, so that the clutch is engaged fordriving the compressor and charging a compressed-air tank, when theengine operation changes from driving to braking. In this manner, thekinetic energy of the vehicle is used to drive the compressor, and aportion of the braking energy, which is otherwise lost as heat in thevehicle brakes, is instead used to drive the compressor. In this manner,the operating time of the compressor when the engine is in drive mode,is reduced.

SUMMARY OF THE INVENTION

The purpose of the present invention is to achieve an internalcombustion engine of the type described by way of introduction, whichmakes it possible, more effectively than what is known, to reduce theoperating time of a vehicle compressed-air compressor when the engine isin drive mode without reducing the capacity of the compressed-airsystem.

This is achieved according to the invention by virtue of the fact thatthe exhaust conduit, at a point upstream of the shutter devicecommunicates with a conduit, which opens, via valve means, into an inletto an compressor.

The invention is based on the idea of using the high pressure, on theorder of 3-4bar arising in the engine exhaust manifold during enginebraking with the exhaust pressure regulator activated, and pre-chargingthe air compressor with this air from the exhaust manifold instead offrom an intake at atmospheric pressure. By allowing the compressor toget its air from the exhaust manifold during engine braking with anactivated exhaust pressure regulator, the capacity of the compressor ismultiplied several times, resulting in the compressed-air tanks beingfilled three to four times more rapidly than in a conventionalcompressed-air system. Since the overpressure used by the compressor iscreated when the engine is in braking mode, no extra fuel is consumed tocreate the overpressure. The reduction in the operating time of thecompressor when the engine is in normal drive node, made possible by thearrangement according to the invention, results in fuel savingscorresponding to what the work of the compressor would have otherwiseconsumed if the compressor had taken its intake air directly from thesurrounding atmosphere.

BRIEF DESCRIPTION OF THE DRAWINGS

The invention will be described in more detail with reference toexamples shown in the accompanying drawings, where

FIG. 1 shows a schematic representation of an internal combustion enginewith an air compressor connected thereto, and

FIG. 2 is a corresponding schematic representation of a somewhatmodified embodiment.

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

1 in FIG. 1 designates a six-cylinder diesel engine with a gearbox 2connected thereto. A turbo-compressor generally designated 3, has itsturbine portion 4 connected to the exhaust manifold 5 of the engine andits compressor portion 6 connected to the engine intake conduit 7, whichopens, via a charge air cooler 7 a, into an intake manifold 8.

The outlet 9 of the turbine 4 opens into an exhaust pressure regulator,generally designed 10, which can be of a type known per se and whichcomprises a shutter housing 11, containing a shutter (not shown) and apneumatic regulator means 12, which is connected to the shutter andwhich is controlled by a regulator valve 13. With the air of theregulator means 12, the shutter of the regulator 10 can be adjustedcontinuously between the completely open and completely closedpositions.

An air compressor, generally designated 14, is drivably coupled to theengine in a known manner which is not shown in more detail here. Bymeans of a regulator system, not shown in more detail here, with amongother things a pressure sensor for sensing the pressure in anaccumulator 15, the engagement and disengagement of the electromagneticclutch means (not shown) of the compressor 14 are controlled.

According to the invention, the compressor 14 has a suction conduit 16,which, via a valve controlled by a control system (not shown in moredetail here) and a conduit 18 with a cooler 19, can be connected to aconduit 20 which opens into the exhaust manifold 5 of the engine 1.

During engine braking, when the engine is driven by the vehicle withoutopening the throttle, the engine functions in principle as an air pumpor compressor pumping clean air from the intake manifold 8 to theexhaust manifold. To increase the braking power, the regulator 10 isclosed, and a pressure on the order of 3-4 bar is created in the air inthe exhaust manifold. If the valve 17 is now placed in a positionconnecting the suction conduit 16 of the compressor 14 to the conduit20, at the same time as the compressor drive is engaged, the compressor14 will be precharged with air from the exhaust manifold at a pressureof circa 3-4 bars. This means, in contrast to when the valve 17 in aposition connecting the suction conduit 16 of the compressor to aconduit 21 opening to the atmosphere, that the accumulator 15, via aconduit 22, will be charged in a third or a fourth of its “normal”period with a corresponding fuel-saving over the case when theaccumulator is charged as the engine drives. Alternatively, theprinciple of the invention can be used to replace a two-cylindercompressor in a conventional compressed-air system with a one-cylindercompressor which is pre-charged with exhaust manifold air. When thecompressed air accumulator 15 need to be filled during normal engineoperation, this is done with the valve 17 in the position in which thesuction conduit 16 of the compressor 14 communicates with the conduit21.

The embodiment in FIG. 2 differs from that described above by couplingan extra pressure accumulator 30 in the conduit 20 between the exhaustmanifold 5 and the valve 17. In those cases when the main accumulator 15during engine braking does not need to be filled up, the accumulator 30can be charged to the exhaust manifold pressure of 3-4 bar. This meansthat there will be a certain air reserve at high pressure availablelater for pre-charging of the compressor during normal engine operation.The arrangement also makes it possible to utilize the exhaust manifoldair in the accumulator 30 for different purposes. It is possible, forexample, during a short period of time, to return the air to the intakeside to provide supercharging in the engine cylinders at low engine rpm,when the charging capacity of the turbo-compressor is poor. Theprinciple of the invention can also be utilized in an engine which can,in itself, function as a compressor by one or more of its cylindersbeing provided with extra valve devices and control means for intake,compression and exhaust of compressed air to a compressed-air tank. Fora more detailed description of such an engine, reference is made, forexample, to SE 467 503 B. In such an engine, the compressed air is ledin the exhaust manifold back to the intake side of the engine forcompression in an additional step before it is fed to the compressed-airtank via said extra valve means. “Air compressor” in the attached patentclaims thus also comprises a compressor in an engine and compressorinstallation, where the compressor function is integrated in theinternal combustion engine itself.

What is claimed is:
 1. An internal combustion engine comprising: anexhaust conduit; a shutter device at an outlet of said exhaust conduitfor regulating exhaust counter pressure in the engine's cylinders duringengine braking; a first conduit having a first end connected to saidexhaust conduit, upstream of said shutter device; and a valve connectinga second end of said first conduit to an inlet of an air compressor. 2.The engine according to claim 1, wherein said valve has a first positionto connect the inlet of the air compressor to said first conduit and asecond position to connect the inlet of the air compressor directly tothe surrounding atmosphere.
 3. The engine according to claim 2, furthercomprising an accumulator tank and a compressed air conduit, saidcompressed air conduit connecting said accumulator tank to an outlet ofthe compressor.
 4. The engine according to claim 2, further comprisingan accumulator tank in said first conduit, between said exhaust conduitand said valve.
 5. The engine according to claim 1, further comprisingan accumulator tank in said first conduit, between said exhaust conduitand said valve.
 6. The engine according to claim 5, further comprisingan accumulator tank in said first conduit, between said exhaust conduitand said valve.
 7. An internal combustion engine comprising: an exhaustconduit; an air compressor that selectively suctions exhaust at higherthan atmospheric pressure from said exhaust conduit and air atatmospheric pressure from a surrounding atmosphere; and a first conduitwith one end directly connected to said exhaust conduit and thatreceives the exhaust at higher than atmospheric pressure and a secondend that provides the exhaust at higher than atmospheric pressure tosaid air compressor.
 8. An internal combustion engine, comprising: anexhaust conduit; a turbo-compressor having a turbine in communicationwith said exhaust conduit; an exhaust pressure regulator incommunication with an outlet of said turbine, said exhaust pressureregulator comprising a shutter and a regulator valve that controls saidshutter through a pneumatic regulator; a first conduit having one endopening into said exhaust conduit upstream of said turbo-compressor; anair compressor; and a valve selectively connecting an inlet of said aircompressor to a second end of said first conduit and a surroundingatmosphere.